Process of making asbestos friction elements



LESTER KIRSGHBRAUN, OF LEONIA, NEW JERSEY,'ASSIGNOR, BY MESNEASSIGNMENTS,

TO RAYBESTQS-MZXNHATTAN, INC

.A CORPORATION OF NEW PROCESS OF MAKING ASBESTOS FRICTION ELEMENTS NoDrawing, Uriginal application filed September 10, 1920, Serial No.409,388. Divided and thisapplicm tion filed October 31,1928. Serial No.31%,344.

This application is a division of my 00- by slippage of the clutch andwhich will not be affected by oils or w ter; to provide a prodnot of theabove character which is tough and more or less flexible and willWithstand brak ing strains; to provide a product in which the saturatinmedium for theashestos com prises an asphalt containing oil which is ormay be heavy Mexican crude which 1s relatively cheap.

Heretofore expensive saturants or binders as linseed'oil and drying oilsthinned down with asoline have been used. This inventionio viates theuse of a drying oil and gasoline and permits of the use of a very cheappetroleum oil, thus markedly reducing the cost of production. i thus usea non-drying mineral oil of asphaltic base such as Mexican crude of 12Baum gravity.

The invention may be carried out as follows: I may first preferably formthe ring of unwoven feltcd'asbestos in the manner set forth in U. S'.Patent No. 1,301,612, issued to S. Simpson, or it may be a moldedunwoven ring. If desired, the woven asbestos covered Wire rings may beused.

These rings are immersed in a tank containing Mexican crude petroleum of.say 12 Baum gravity which has been thinned or cut back with about-20%of gas oil, as for example, mid-contincntal gas oil of from 32 to 34Baum. -The use of thisrather volatile gas oil facilitates saturation andtends to prevent the asphaltic oil from bleeding out of the ring duringthe baking operation herein after described. The contents of the tankare heated to about350 R, and the rings kept the tank about two hours.The rings are then removed and the excess ofsaturant allowed to drainfrom the rings while the rings are still kept in a heated condition notbelow 200 F.

At this stage the ringswill have taken up about 35% to 40% by weight ofsaturant.

The rings are then transferred to a baking oven and there subjected to abaking operation. Starting with a temperature of about 300 F. theheat inthe oven is slowly and .gradually raised over a period of approxiing. Atthis stage of the curing, the rings are still relatively soft and weakand the asphalt is still also soluble in the usual solvents.

After the temperature of 550 F. has been reached the curing is continuedfor 24 to 48 hours additional treatment at the same temperature.

At the end of the second sta e of the baking operations, the asphalt hascon so altered that it is entirely insoluble in the usual solvents suchas kerosene or carbon tetrachloride. The length of the baking operationis deter- .mined by testingone of the rings with the above solvents.

These rings have all of the advantages and characteristics. heretoforeset forth in the ob. jects of invention. The finished rings have aBrinell hardness of from 15 to 25 and a ten- 1 sile strength upwardsfrom 2000 to 3000 pounds per square inch. Care should be taken duringthe curing operation to keep the temperature uniform and particularly anexcessive temperature (much above 600 should be avoided. The volatilizedand oxi- The following specific illustration of actual operation of theinvention may also be given. The dry asbestos rings, after beingcalendered were saturated for a period of about one hour in heavyMexican asphaltic residuum contained in a vehicle of mid-co'ntinentalpetroleum gas oil. About 80% of the Mexican residuum was used to about20% of gas oil. The gas oil not. only facilitates saturation butprevents the surface ofthe rin from being prematurely sealed ofi oninitial baking and polymerization of the asphalt. In otherwords, the gasoil prevents a surface baking which will prevent the heat from enteringthe interior of the ring. The saturating solution was heated to atemperature of about 300 F. and the rings kept in the tank for one hour.The rings were then removed and put into the baking oven, starting witha temperature of 200 F. and was steadily raised to a temperature of 500F. in five hours and held at such temperature for about vtwelve hours.-

The rings were then removed and resaturated in a similarsaturatingsolution and then rebaked as before except that thetemperature was started at about 500 F. and the rings baked for abouttwelve hours.

The rings were then put into a press and squeezed together. tostraighten them out and kept in the press until cooled.

The rings made in this manner have a ten sile strength-of approximately2000 where a double saturation and double baking were used and a Brinellhardness of over 20. Where onlyone saturation and one baking is used thetensile strength and Brinell hardness will be considerably less.

Rings made in the same way as the above except that the asbestos pulpcontained lead oxide with double saturation and double baking, had atensile strength of about 2700 and approximately 20Brinell hardness andwhere a single saturation and single baking were used a veryconsiderable less amount of tensile strength was obtained. Where doublesaturation was used the overa e percent of saturation relative to theweig t of the dry rings was about 20%, more or less.

It is to be clearly understood that the invention may be carried out inthe manner described in said former application which is made a part ofthis present application but that the illustrative operation given showsan actual carrying out of the process.

I claim as my invention: A process Wl'llCl'l comprlses saturating anunwoven felted asbestos mass in a'bath of heated asphaltic base oil,then subjecting said saturated mass to a baking operation at an elevatedtemperature, thereafter resaturating said mass in a bath of similarsaturant, and thereafter subjecting the mass to a final baking operationat an elevated temperature continued until the saturantis substantiallyinsoluble in asphaltic solvents.

"In testimony whereof I aflix my signature.

LESTER KIRSCHBRAUN.

